The rear rollers took less than 5 mins each- tilt the frig against a wall, unscrew the single hex head bolt one at a time just behind each roller, when the frame drops down slide the pin out, replace the roller, and reinsert that bolt. Done.
The front roller is a little tougher, in hindsight I'd recommend replacing the entire adjustable assembly; it's more expensive but much easier. To replace the roller alone I had to work the bucked end of each roller axle down to the same diameter as the axle so it could then slide out of the housing and a new roller put in place. Re-mushrooming that end of the pin is a challenge once the roller is in place, but not insurmountable just time-consuming.